It is really a personal preference. If you sensitive ears I would suggest the M21 since the M11+ can be a little harsh. At the price of the M11+ I would spend the extra for the E10. After reading about it a little it should be better than both the M21 and M11+.

I picked up a pair of M6P in a recent sale and noticed a few design changes worth mentioning. One is a switch from the 45 degree jack to a 90 degree jack. The other is the redesign of the remote/mic piece. It not includes a dedicated button (apposed to the whole piece being one big button before) and strain reliefs on the either end of the remote/mic. It remains to be seen how well these improvement actually preform, but they do seem to be attempts at fixing a few of the problems I had with the "P" models from MEElectronics. On the downside, the driver flex is annoying. Strangely, both clear M6 I have had have had no driver flex while all three black M6P I have had driver flex. IDK not know if the color has any affect or if it was just purely luck.

UPDATE: I have been comparing my old M6 to my newer M6P and noticing they sound different. My initial though was that is was just effect hours of burn in (actually just many hours of use) on the older M6. However, the M6P have been given plenty of hours of burn in and they still sound different. The older M6 has a lot of bass, but not overpowering on most songs. It is tight and clean. The newer M6P has pounding bloated bass that overpowers the mids. The mids on the newer M6P lack the detail and clarity of my older M6. That could just be to the bass drowning them out. The treble on the newer M6 might actually be better. Does not sound quite as harsh. However, turning my head or tilting it up or down causes the treble to disappear. My old M6 did this too and I assumed it a was fit issue until one day it stopped. I assumed I had just finally found the right fit. Seeing has how I am using the exact same tips on this newer M6P as I do on my older M6 and I am once again having issues with the treble I am wondering if there is something going on hear besides just getting a poor fit. The difference in bass makes me wonder if the M6 driver has changed over the years. The issue of disappearing treble just makes me wonder if I just plugged in the new M6P and burned it in even longer if maybe it would change like the old M6 did. Might have to contact MEElec and see if they have any comments.

EDIT: MEE says the M6 is still using the same driver, however the tuning has been tweaked to add more bass and reduce the treble--which sounds about like what I said. I think the treble reduction was an improvement. The added bass is a bit much for my taste though. Probably something EQ can fix, but might be something you want to keep in mind if you read old reviews of the M6 like mine that the tuning has been changed to add more bass.

Any body can compare these two Teknofusion Twinwoofers and Audio Technicia ATH M50 ?

I do own the ATH-M50. Simply put the M50 blows them all out of the water. As it should at five times the price. The M50 and the M6 do both share a similar v-shape signature though. I suppose if you are looking for a cheap pair of IEMs that sound similar the M50 you could worse than the M6.